1. Field of the Invention
The present invention relates to a position adjusting method and position adjusting system of color combining optical system for adjusting position of the color combining optical system relative to optical component casing which accommodates optical components constituting a color separating optical system of a projector, a color combining optical system adjusted by the position adjusting method, a position adjusting method and position adjusting system of optical modulator for adjusting relative position of a plurality of optical modulators of a projector, and a projector adjusted by the position adjusting method.
2. Description of Related Art
Conventionally, a projector for modulating a plurality of color lights in accordance with image information to project on a screen through a projection lens has been known, which is widely used for multimedia presentation at conference, academic society, exhibition etc.
So-called three-plate projector having a color separating optical system for separating a light beam irradiated by a light source into three color lights of red, green and blue by a dichroic mirror, three optical modulators for modulating the separated light beam for each color light in accordance with image information and a cross dichroic prism for combining the light beam modulated by the respective optical modulators is known as such projector.
The optical components such as the dichroic mirror constituting the color separating optical system and a lens array constituting uniform illuminating optical system are accommodated in an optical component casing established with an optical path extending from the light source to the optical modulator. The optical component casing is composed of an upper casing having a recess for the optical components to be mounted and a lower casing for shutting the lower side of the upper casing. A lens attachment for attaching the projection lens is provided to the lower casing at an end of the optical path.
The three optical modulators are directly attached to a light-incident end surface of the cross dichroic prism. A fixing plate is adhered and fixed to the lower side of the cross dichroic prism attached with the optical modulator and is fixed at the front of the optical path of the projection lens on the lower casing by a screw using a threaded hole formed on the fixing plate.
Such arrangement is adopted because, in fixing the optical modulator on the light-incident end surface of the cross dichroic prism, the relative position of the respective optical modulators has to be determined with high accuracy in order to avoid shift of picture elements etc. Conventionally, the step for accommodating the optical components within the casing and the step for fixing the optical modulator to the cross dichroic prism are independently conducted and both components are combined in the final step.
However, according to the conventional method, appropriate projection image may not be obtained according to dispersion of disposed position of the optical components and inner optical components and fixing position of the fixing plate to the cross dichroic prism. Specifically, when the fixing position of the cross dichroic relative to the fixing plate is shifted, since the fixing plate is fixed to a predetermined position of the lower casing by the screw, the position of the cross dichroic prism is also fixed in accordance therewith. Therefore, the adjustment of the cross dichroic prism in line with the optical axis of the light beam established in the optical component casing is impossible and the color lights cannot be appropriately combined, thereby deteriorating the quality of images projected by the projection lens.
An object of the present invention is to determine the position of the color combining optical system of a projector with high accuracy.
Further, smaller optical modulator is used for recently developed small projector, where the optical path from the light source to the projection lens is shortened and beam-condensation rate of the light of the light source is decreased, so that illumination margin tends to be decreased. Accordingly, in the conventional method where the step for producing the optical component casing and the step for fixing the optical modulator to the cross dichroic prism are separately conducted and the position of the components are adjusted in assembling the both of the components at the final stage, the position of the both assembled components has to be adjusted with small illumination margin, so that there is certain limit in adjustment accuracy.
Another object of the present invention is to cope with the decrease in illumination margin in accordance with size reduction of a projector in adjusting the position of optical modulator.